Measles encephalitis was produced in 41 hamsters by intracerebral injection of the hamster-neuroadapted Mantooth HBS viral strain. Group I (n=10) included 2-day old (newborn) hamsters, each inoculated with 0.02 ml of 1:20 diluted virus. This group was sacrificed 4 days postinoculation (DPI). Group II (n=31) included 25-day old hamsters, each inoculated with 0.03 ml of 1:10 diluted virus. This group was sacrificed 6, 13, 17, and 31 DPI. Clinical and histological evidence of measles encephalitis was present in all infected hamsters. Retinal lesions varied with the age of the animals at the time of inoculation. Retinal folds were observed in the 2-day old group and represented one form of retinal dysplasia. In the 25-day old group, however, earliest retinal involvement was in the form of hemorrhages, followed by focal retinitis in animals sacrificed 6-17 DPI. Measles keratitis was noted only in animals sacrificed 6 DPI. In 25-day old hamsters, measles keratitis and retinal hemorrhages represented the acute manifestations, whereas retinitis occurred later. However, ocular involvement did not correlate with the degree of severity of measles encephalitis.